Device for stretching pieces of tube



1929- P. F. HELLERMANN ,7

DEVICE FOR, STRETCHING' PIECES OF TUBE Original Filed July 27, 1925 2 Sheets-Sheet l 1929- P. F. HELLEIRMANN 1,725,638

DEVICE FOR STRETCHING PIECES OF TUBE Original Filed July 27, 1,925 2 Sheets-Sheet 2 Patented Aug. 20, 1929 UNITED STATES 1,725,638 PATENT OFFICE.

PAUL rnmnnrcn HELLERMANN, or HAMBURG, GERMANY.

DEVICE non srnn'rcnmo minors or TUBE.

Original application filed July 27, 1925, Serial No. 46,474, and in Germany February 9, 1925. Divided and this application flled January 21, 1927. $erial No. 162,660.

If insulated electrical conductors or cords are to be connected to a switch or a source of current or to an implement or utensil which 1 consumes electric current, theend or ends of the metallic conductors must first be laid bare. For this purpose it is necessary to remove for a suitable length the silk or other insulation. The usual consequence is that the fibrous ends ofthe insulation which still remains on the 1 conductor form a tangle which, if care be not taken, will gradually lead to further displacement of the insulation or to unraveling of the threads or fibres. That is, the insulation must be bound again at the bared portion not only for the sake of appearances but in the interest of security. For this purpose there were heretofore used binding threads, insulating tapes or the like which were wound around the insulation and secured by adhesive or knotted. If the binding be notdrawn tight, there is no effective security against subsequent displacement of the insulation. Also knots and fastenings eifected by adhesive readily give way. The like is true if bare parts of electrical conductors the ends of which are wound together are to be insulated. Now, the subject of the present application which is a division of my pending application Ser. No. 46,474 filed July 27, 1925, is a device which is adapted to be used for binding such insulated conductors or bare electrical conductors requiring to be insulated. By means of this device apiece of rubber tubing or the like cut to asuitable transversely in at least two different directions, and after insertion of the conductor as far as it is to be covered by the binding, or as far as the insulation is to extendthe stretching eflort is discontinued to allow the tubing to tensionally grip the conductor. The bore of the tubing is, if possible, such that the piece of tubing not only embraces an end of the insulation as well as the adjoining bared portion of the conductor, having suificient tension to grip the naturally thinner end of wire.

In the accompanying drawing the device is shown in Fig. 1 in plan, and in Fig. 2 in side elevation. v Figs. 3 and 4 are an elevation and a plan of an accessory for use with the device shown inFigs. 1 and 2. j

7 length and of minimum bore is stretched Figs. 5 to 13 illustrate the various stages of operatlon in the use of the instrument.

- F 1g. 14 shows two conductor sections bound according to the invention.

The pliers-like instrument shown in Figs. 1 and 2 consists of two jaws b ivoted at a and adapted to be moved apart y gripping together the handle members a. A spring d mounted on two curved guide members e fixed to the handle members urges the jaws towards one a nother. The jaws can be detained in the position corresponding to the compressed posit on of the spring by a clas member f comprising two arms and pivote at g to one handle a, being subject to the influence of a spring h. The jaws I) each carry one half of each of two impaling pins h and i which are somewhat rounded at one end so that they can be readily introduced into the tubing. When the handles are brought together, the half portlons of the impaling pins move apart. The pin it is in toto thinner than the pin 13. Associated with this instrument is the accessory shown in Fig. 3. The latter consists of a corrugated sheet metal plate or strip m from one lateral edge of which project two pins 11. and from the other lateral edge of which project two pins 0, the pins being parallel to a line constituting the generatrix of said arched portion. The pins 0 are spaced further apart than the pins 02. If desired the corrugation k may be curved to shorter radius near the pins n than near the pins 0.

The mode of use of the instrument is as follows:

First, as shown in Fig. 5, the stretcher is held in one hand while with the other hand a plece of tubing p is impaled on the split impahng pin 2', bein preferably slightly expanded or stretche This piece of tubing is cut from a rubber tube the bore of which, if to receive insulated conductors of 6 millimetres diameter, amounts to about 1 to 2 millimetres, and the wall of which is sufficiently strong to permit the necessary expansion. When this is done, the handles '0 are compressed so that the tubing is powerfully stretched in one direction. Then the accessory instrument m is inserted in the expanded tube, thus for exam Ie, the pins 0 are inserted the spacin of t e pins 0 being less than the s acing of the halves of the pin z when move apart (Fig. 7). Then, as shown in Fig. 8, the instrument m is turned through 90, so that the tubing is stretched in two directions at right angles to each other. The instrument m can now be released without its returning toinitial position. Guided by the corrugation k a cord 1 presenting a tassel s of insulation formed by exposing the bared ends of the conductors can now be introduced into the tubing which has been stretched in two directions-see Figs. 9 and 10. Then, as shown in Fig. 11, the instrument m is reversely turned through 90 into Fig. 7 position. The tube ;0 now grips the conductor 7 at two sides and holds it securely. The conductor can thus be released and the instrument m withdrawn from the tube. Then the stretcher handles 0 are so released as to allow the halves of the pin '11 to come together (Fig. 12), the conductor 1" beingnow gripped by the tubeand disengaged from the stretchers (Fig. 13). The binding operation is thus completed.

Such bindings are illustrated in Fig. 14. As shown, not only the insulated portion but also parts of the protruding wire ends are embraced by the tubing, though this is not necessary. Also bared conductor ends can be insulated by means of a piece of tubing applied in this way, or connected cords can be separatively sleeved by tubing as shown.

Ads is understood, the stretchers can be used for all cases where pieces of tubing require to be stretched.

I claim 1. A device for stretching pieces of tube particularly for the purpose of covering the junction between the bared end and the insulated portion of an electrical conductor,

tubingparticularly for the purpose of encompassing an electric conductor with said tubing under permanent tension, comprising pliers ofthe type in which the jaws open when the handles are pressed together, a pin projecting laterally from said jaws in a direction substantially parallel to the pivotal axis of said pliers, said pin being longitudinally divided forming mating halves, one carried by'each jaw, and which move apart when said jaws are separated, a spreading member adapted to fit the space between said halves, and a latch comprising parts mounted on said handles engageable when said jaws are spread to hold the halves of said pin in a definite spread position in Which said spreading member fits between them.

Intestimony whereof I have signed my name to this specification.

IAlll. FRIEDRICH HELLERMANN.

2. A device for stretching pieces of elastic I 

